The present invention relates to fastener systems for use primarily in securing together layered or honeycomb panels, and more particularly relates to fastening of panels which may be relatively soft or delicate and of the type used in aircraft and aerospace applications.
In aircraft and other construction, rivet-type fastener locking has been employed to clamp securement of multi layer panel assemblies in which a soft core requires controlled compression in the fastener assembly, as described for example in U.S. Pat. No. 3,459,447, to avoid over clamping and damage to the panels. Further development has lead to blind rivet fasteners as described in U.S. Pat. No. 4,919,576 in which formation of the blind rivet also employs a separate "anvil washer" tool to deform the internal locking collar of the rivet. One of the panel clamping surfaces of the rivet fastener is created by swaged deformation of the portion which engages one of the panels, and the swaging formation represents potential damage to the panel surface and the integrity of the panel assembly. These and other disadvantages are eliminated by fastener structures in accordance with the present invention.